1. Technical Field
The present invention relates generally to a distance sensor with a compact and easy-to-install structure of an electrical connector which may be used with an obstacle detection system for vehicles.
2. Background Art
Ultrasonic sensors are known which are used as automotive distance sensors (also called range sensors) which measure the distance between the vehicle and an obstacle using an ultrasonic wave. Some of modern vehicles such as automobiles are equipped with an obstacle detector called a clearance sonar system for assisting the driver in parking the vehicle. The clearance sonar system has a plurality of ultrasonic sensors (e.g., two installed in a front bumper, and four installed in a rear bumper) and works to measure the amount of time required by the ultrasonic wave, as transmitted from each of the ultrasonic sensors, to travel to and return from an obstacle and determine the distance between the vehicle and the obstacle based on the measured amount of time. When such a distance decreases below a given value, the clearance sonar system alerts the driver by sound.
FIGS. 12(a) and 12(b) illustrate an example of electrical connections between ultrasonic sensors used in the above type of a clearance sonar system. The ultrasonic sensors are connected in series to an electronic control unit (ECU) through harnesses each of which is equipped with ground, serial-communication, and power supply cables. Each of the ultrasonic sensors has an input and an output terminal (denoted by “IN” and “OUT” in the drawing) to which the power supply cables are joined for the daisy-chain connection of the ultrasonic sensors. A connector of each of the ultrasonic sensors, therefore, has at least four conductive terminals. In case of four conductive terminals, the two ground cables need to be tied and joined, as indicated by numeral 91, to one of the terminals of the connector. The same applies to the serial-communication cables. This results in an increase in production cost of the harnesses. In order to avoid this drawback, the connector of the ultrasonic sensor may be, as illustrated in FIG. 12(b), designed to have six conductive terminals. In this case, a circuit board of the ultrasonic sensor has to have two electric joints 92.
The above six-terminal structure of the connector is useful for cost reduction of the harnesses, but will lead to an increase in overall size of a casing 45′ of an ultrasonic sensor 3′, as illustrated in FIG. 13. This also results in increased constraints on installation of the ultrasonic sensor 3′ in a bumper 2 of the vehicle. Particularly, it becomes difficult to insert the casing 45′ into a mount hole 47 of the bumper 2, thus requiring the need for disassembling the ultrasonic sensor 3′ into two parts: a bezel 49′ and the casing 45′. This results in an increase in time consumed to fix the ultrasonic sensor 3′ to the bumper 2.
Japanese Patent First Publication No. 6-176822 (corresponding to U.S. Pat. No. 5,516,299 filed on Dec. 7, 1993) discloses the above type of a multi-input connector.